Grade 7
  1. Introduction to Chemistry  1.1. What is Chemistry?  1.2. Importance of chemistry in daily life  1.3. Branches of chemistry  1.4. Scientific Method in Chemistry  1.5. Laboratory Safety Rules and Precautions  1.6. Common Laboratory Equipment and Their Uses  1.7. Units of measurement in chemistry
  2. Matter and its properties  2.1. Definition of Matter  2.2. Classification of matter  2.3. Properties of matter  2.3.1. Physical properties  2.3.2. Chemical properties  2.4. States of matter  2.4.1. Solid state  2.4.2. Fluid state  2.4.3. Gaseous state  2.4.4. Plasma and Bose–Einstein condensates  2.5. Changes in the states of matter  2.5.1. Melting and freezing  2.5.2. Evaporation and Condensation  2.5.3. Sublimation and deposition  2.6. Density and its applications  2.7. Diffusion and its importance
  3. Elements, Compounds, and Mixtures  3.1. Definition of the element  3.2. Classification of elements  3.3. Metals, Nonmetals and Metalloids  3.4. Noble gases and their properties  3.5. Introduction to the Periodic Table  3.6. Definition of Compound  3.7. Properties of Compounds  3.8. Introduction to Chemical Formulas  3.9. Definition of Mixture  3.10. Types of mixtures  3.10.1. Homogeneous mixture  3.10.2. Heterogeneous mixtures  3.11. Difference Between Compounds and Mixtures  3.12. Solutions, Colloids and Suspensions
  4. Separation of mixtures  4.1. Need for separation of mixtures  4.2. Separation methods  4.2.1. Filtration  4.2.2. Sedimentation and decantation  4.2.3. Evaporation  4.2.4. Crystallization  4.2.5. Distillation  4.2.6. Chromatography  4.2.7. Magnetic Separation  4.2.8. Centrifugation
  5. Atomic Structure  5.1. Introduction to Atoms  5.2. Structure of the atom  5.2.1. Nucleus and electron cloud  5.3. Subatomic particles  5.3.1. Proton  5.3.2. Neutron  5.3.3. Electrons  5.4. Atomic number and mass number  5.5. Isotopes and their uses  5.6. Ions and ion formation
  6. Periodic table  6.1. Introduction to the Periodic Table  6.2. Groups and periods  6.3. Trends in the Periodic Table  6.3.1. Atomic Size  6.3.2. Metallic and non-metallic character  6.3.3. Electronegativity  6.3.4. Reactivity of the elements  6.4. Alkali metals and their properties
  7. Chemical bond  7.1. Why do atoms form bonds?  7.2. Types of chemical bonds  7.2.1. Ionic bond  7.2.2. Covalent bond  7.2.3. Metal Bond  7.3. Properties of Ionic and Covalent Compounds  7.4. Intermolecular forces
  8. Chemical reactions  8.1. Introduction to Chemical Reactions  8.2. Signs of a chemical reaction  8.3. Types of Chemical Reactions  8.3.1. Combination Reactions  8.3.2. Decomposition reactions  8.3.3. Displacement reactions  8.3.4. Double displacement reactions  8.3.5. Combustion reactions  8.4. Law of conservation of mass  8.5. Balancing simple chemical equations
  9. Acids, Bases and Salts  9.1. Definition of Acid and Base  9.2. Properties of Acids  9.3. Properties of bases  9.4. pH Scale and Indicators  9.5. Neutralization reactions  9.6. Common Acids and Bases in Everyday Life  9.7. Preparation and use of salts  9.8. Strong and weak acids and bases
  10. Solutions and Solubility  10.1. Definition of Solution  10.2. Components of the solution  10.2.1. Solvent  10.2.2. solute  10.3. Factors Affecting Solubility  10.4. Concentration of solutions  10.5. Saturated and unsaturated solutions  10.6. Colloids and suspensions  10.7. Solubility curve and its interpretation
  11. Air and atmosphere  11.1. Composition of air  11.2. Properties of gases in the air  11.3. Importance of Oxygen and Carbon Dioxide  11.4. Air pollution and its effects  11.5. Greenhouse effect and global warming  11.6. Ways to reduce air pollution  11.7. Ozone layer and its importance
  12. Water and its importance  12.1. Properties of Water  12.2. Water as the universal solvent  12.3. Importance of water for life  12.4. Water pollution and its effects  12.5. Water Purification  12.5.1. Filtration  12.5.2. boil  12.5.3. Chlorination in water purification  12.5.4. reverse osmosis  12.6. Hard and soft water  12.7. Water cycle and its importance
  13. Fuel and energy  13.1. Types of fuel  13.1.1. Fossil fuels  13.1.2. Renewable energy sources  13.2. Combustion and energy release  13.3. Global warming and its effects  13.4. Alternative sources of energy  13.5. Ways to conserve energy
  14. Metals and Nonmetals  14.1. Physical and chemical properties of metals  14.2. Physical and Chemical Properties of Non-Metals  14.3. Difference Between Metals and Nonmetals  14.4. Uses of metals and nonmetals  14.5. Corrosion of metals and its prevention  14.6. Alloys and their importance
  15. Plastics and polymers  15.1. Natural and synthetic polymers  15.2. Properties of plastics  15.3. Biodegradable and Non-Biodegradable Plastics  15.4. Environmental impact of plastic  15.5. Recycling and waste management in plastics and polymers  15.6. Daily Uses of Polymers
  16. Introduction to Organic Chemistry  16.1. Basic definitions of organic chemistry  16.2. Carbon Compounds in Daily Life  16.3. Hydrocarbons  16.4. Simple functional groups (alcohols and carboxylic acids)  16.5. Importance of organic compounds in industry

Grade 7 ↓


Separation of mixtures


In chemistry, we often have to separate mixtures into their individual components. A mixture is a combination of two or more substances, where each substance retains its chemical identity and properties. There are many ways to separate mixtures, and the choice of method depends on the type of mixture and the properties of its components. In this lesson, we will explore various separation techniques such as filtration, evaporation, distillation, and others.

What is a mixture?

A mixture is made up of two or more substances that combine physically, but not chemically. This means that each substance in the mixture keeps its own properties. For example, when you mix sand and salt, you can see individual particles of sand and crystals of salt. They do not form a new substance.

Mixtures may be homogeneous or heterogeneous:

  • Homogeneous mixtures have exactly the same composition. An example of this is salt dissolved in water.
  • Heterogeneous mixtures have different compositions in different parts. An example of this is a mixture of oil and water.

Why do we separate mixtures?

We separate mixtures to obtain different components for various purposes such as purification, separation, and others. For example, salt has to be separated from water to obtain drinkable water from seawater.

Separation methods

Filtration

Filtration is a method used to separate an insoluble solid from a liquid. A common example is separating sand from water. When you pour a mixture of sand and water through a filter paper placed in a funnel, the sand stays on the filter paper while the water passes through it in the form of filtration.

In this instance, the solid particles are trapped by the filter paper, allowing only the liquid to pass through. This method is widely used in laboratories and for household purposes such as making coffee.

Evaporation

Evaporation is used to separate a soluble solid from a liquid. For example, if you have a salt water solution, you can heat the solution until the water evaporates and the salt is left behind.

This method is simple and effective for separating mixtures such as salt water.

Distillation

Distillation is used to separate a liquid from a solution. This method uses differences in boiling points to separate the components. For example, water can be separated from salt water by boiling the solution until it boils into vapor. The vapor is then cooled and condensed back into liquid water, leaving the salt behind.

Water (H 2 O): Boiling point = 100°C 
Salt (NaCl): Boiling point = around 1465°C

This ability to separate based on boiling point is why distillation is used to purify liquids, such as separating drinking water from seawater.

Chromatography

Chromatography is a technique used to separate the different components of a liquid mixture. This method is often used in laboratories to analyze mixtures of substances. It works based on the different speeds at which substances move through a medium.

Each color represents a different component of the mixture. Since they move at different speeds, they separate out along the medium.

Magnetic separation

Magnetic separation is used to separate magnetic substances from non-magnetic substances. For example, if you have a mixture of iron filings and sand, you can use a magnet to remove the iron filings.

The magnetic field of the magnet attracts the iron filings, causing them to separate from the sand.

Examples and exercises

Let's look at some examples and practice questions so we can better understand how these separation methods work.

Example 1: You have a mixture of sand and iron filings. Which separation method would you use?

Since iron filings are magnetic and sand is not, you will use magnetic separation to remove the iron filings with the help of a magnet.

Example 2: Your task is to obtain pure water from a salt water solution. Which method will you use?

Distillation would be appropriate here. By heating the solution, you can evaporate the water and condense it, leaving the salt behind.

Exercise: Use the following scenarios to test your understanding of separation methods:

  • A mixture of chalk powder and water.
  • A mixture of oil and water.
  • A mixture of sugar and sand.

Try to determine which separation method is best for each mixture.

Conclusion

In short, separation of mixtures is an important concept in chemistry that allows us to separate and purify different components. Whether it is a case of cleaning up oil spills with various techniques or obtaining pure substances for laboratory purposes, it is invaluable to understand how to effectively separate mixtures. The choice of method depends on the physical and chemical properties of the components involved. From filtration and evaporation to distillation and chromatography, each technique serves a unique purpose and has applications in diverse fields.

We hope this guide has given you a solid foundation for understanding the basic methods of separating mixtures. With continued practice and exploration, these concepts will become even more clear and practical to you.


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Separation of mixtures

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